Light, Sound and Force

The Hook (The Mystery & Discovery)

A. Imagine if you woke up in a world of absolute, pitch-black darkness where even the most vibrant colors completely vanished! We are only able to see the beautiful things around us because of a speedy, silent traveler called light, which journeys across the universe in a perfectly straight line. B. Did you know that even though the Moon glows with a gentle, silvery radiance in the night sky, it is actually a cosmic imposter with absolutely no light of its own? It is a non-luminous object that functions as a colossal celestial mirror, simply reflecting the brilliant light emitted by the Sun. C. Imagine if you stood on the Moon’s surface and screamed at the top of your lungs, but absolutely no sound came out! Since sound is produced strictly by vibrating objects and requires air to travel, the complete absence of air on the Moon means sound cannot travel there, leaving you in eternal silence. D. Did you know that every single movement you perform—from pulling a heavy trolley to pushing open a door—is ruled by an invisible, silent powerhouse called force? This push or pull is the universal scientific engine that dictates how objects move, stop, or change their direction and shape.

Real-World Lesson (Why This Matters)

This chapter serves as the fundamental physical blueprint of our daily environment and modern society:

The Power of Light: Without light, human vision is impossible. The Sun acts as the primary driver of our ecosystem, being the main source of light on Earth. Understanding how light travels in straight lines and is blocked to form shadows is the foundation of modern architectural planning, solar energy capture, navigation, and timekeeping technology.
Acoustic Responsibility: Knowing how sound is produced and transmitted helps us navigate our sensory world. It teaches us the critical boundaries between healthy acoustic environments and noise pollution. Loud and unpleasant sounds (noise) are physically harmful to human health and disruptive to community well-being. By practicing personal acoustic management—such as speaking softly, keeping television and music volumes low, and avoiding the use of horns—we actively protect public health and create more harmonious modern societies.
Harnessing Physical Mechanics: Every machine, vehicle, and physical task in modern society relies on the application of force. When we push a door or pull a trolley, we are applying mechanical force. By understanding how force alters motion, speed, direction, and shape, engineers can design safer cars, efficient transit systems, robust buildings, and ergonomic tools that drive global technology forward.

Activities for Experiential, Interactive, and Experiential Learning

To make these concepts tangible and memorable for young learners, teachers can implement these hands-on, interactive classroom activities:

“The Mystery Soundbox” (Experiential Guessing Game):
- Activity Setup: Group students into pairs. Gather diverse everyday items such as paper, spoons, cardboard, wood, plastic, pens, coins, and glass.
- How to Play: Set up a physical screen (like a large cardboard sheet or folder) between two students. One student sits on the opposite side of the screen and makes sounds by striking, tapping, or rustling the collected materials. The other student must listen carefully and guess which specific material is producing the sound.
- Learning Outcome: Teaches students that different materials produce distinct sounds through vibrations and sharpens auditory discrimination.
“Wall Shadow Puppetry and Scale Analysis” (Interactive Experiment):
- Activity Setup: Darken the classroom and provide students with a bright flashlight or torch.
- How to Play: Ask students to cast shadows of their hands or small objects onto a blank wall. Instruct them to move their hands closer to the light source, and then farther away, observing the resulting changes in shadow size.
- Learning Outcome: Directly demonstrates that shadows are formed when an object blocks the path of light, and teaches how the distance from a light source alters the shadow’s scale.
“The Great Sundial Yard Investigation” (Experiential Field Study):
- Activity Setup: On a sunny day, take students outdoors at three distinct intervals: early morning, exactly at noon, and in the late afternoon.
- How to Play: Have each student stand in the same spot and measure the length and direction of their shadow using a measuring tape. Record the findings in a table.
- Learning Outcome: Students observe firsthand that shadows change their size and position during the day according to the shifting position of the Sun in the sky. They learn that shadows are always projected on the opposite side of the light source.
“The Tactile Clay and Toy Car Force Workshop” (Hands-on Exploration):
- Activity Setup: Provide each student or small group with a toy car and a lump of modeling clay.
- How to Play:
  - Part 1 (Movement): Instruct students to push the toy car to make it move, apply a frontal push to stop it, and push it from the side to change its direction.
  - Part 2 (Deformation): Instruct students to squeeze, press, or pull the modeling clay to see how its structure changes.
- Learning Outcome: Solidifies the four major physical effects of force: moving an object, stopping a moving object, changing its direction, and changing its shape.
“The Silent Bell Jar Simulation” (Role Play & Concept Demonstration):
- Activity Setup: Have students roleplay as astronauts landing on the Moon.
- How to Play: Use a sealed vacuum bag containing a small ringing alarm clock or bell. Gradually pump the air out and observe the sound fading to a complete whisper. Discuss why “astronauts” must use specialized communication devices.
- Learning Outcome: Proves visually and conceptually that sound requires air as a medium to travel, explaining why sound cannot travel on the Moon’s airless surface.

Diagrams & Maps: Visual Instruction & Labeled Schematics

Teachers and students can draw and label the following visual aids to reinforce the chapter’s physical concepts:

1. Luminous vs. Non-Luminous Object Classification Schematic

Description: A side-by-side comparative diagram illustrating how light travels from a source to make non-luminous objects visible to the human eye.
Labeled Components:
- Natural Luminous Source: A drawing of the radiating Sun emitting straight light rays.
- Human-Made Luminous Source: A drawing of a burning candle or a glowing lamp emitting light rays.
- Light Rays (Incident Rays): Straight, non-bending arrows indicating the path of light.
- Non-Luminous Objects: Drawings of a watch, pen, pencil, table, and chair.
- Reflected Light Rays: Straight arrows bouncing off the non-luminous objects.
- Human Eye: The receiver detecting the reflected light.
Scientific Concept: We can see non-luminous objects only when light from a luminous source falls on them and enters our eyes.

2. The Diurnal Shadow Variation Chart

Description: A landscape diagram depicting how a static object (e.g., a vertical wooden stick) casts different shadows depending on the Sun’s position.
Labeled Components:
- Morning Sun: Positioned low on the left (East).
- Long Morning Shadow: Cast far to the right (West).
- Noon Sun: Positioned directly overhead.
- Short Noon Shadow: A small, stubby shadow cast directly beneath the stick.
- Evening Sun: Positioned low on the right (West).
- Long Evening Shadow: Cast far to the left (East).
- Opposite Projection Principle: A label highlighting that shadows always form on the opposite side of the light source.
Scientific Concept: Shadows change size and position throughout the day based on the Sun’s position.

3. Sound Production and Transmission Model

Description: A diagram explaining the mechanical nature of sound wave creation.
Labeled Components:
- Striking Tool (Spoon): Moving to strike.
- Vibrating Surface (Steel Plate): Depicted with rapid wavy lines indicating continuous motion.
- Air Molecules (Medium): Shaded dots representing air.
- Sound Waves: Expanding concentric arcs moving from the plate.
- Receiver (Human Ear): The destination of the sound waves.
- No Medium Warning (Moon Comparison): A secondary bubble depicting the Moon with crossed-out air molecules and crossed-out sound waves to represent a vacuum.
Scientific Concept: Sound is produced by vibrating objects and requires air to travel.

4. The Four Effects of Force Map

Description: A four-quadrant concept map illustrating how force changes the physical state of objects.
Labeled Components:
- Quadrant 1 (Move): A boy pushing a heavy door. Label: “Force can move an object at rest”.
- Quadrant 2 (Stop): A hand catching a moving ball. Label: “Force can stop a moving object”.
- Quadrant 3 (Change Direction): A bat hitting a ball or a hand pushing a moving toy car sideways. Label: “Force can change the direction of a moving object”.
- Quadrant 4 (Change Shape): A hand squeezing a soft ball or a lump of dough. Label: “Force can change the shape of an object”.
Scientific Concept: Force is a push or pull that alters an object’s state of motion, direction, or physical shape.

The Exhaustive Sequence / Process / Timeline

The physical sciences operate on strict, logical, and cause-and-effect chains.

Sequence A: The Logic of Sight (How We Perceive Our World)

Emission: A luminous object (such as the Sun, stars, lamp, or candle) emits light of its own in the form of straight rays.
Straight-Line Propagation: These light rays travel outwards in a perfectly straight line. They cannot bend around obstacles.
Collision & Reflection: The straight-moving light rays strike a non-luminous object (such as a book, chair, or watch).
Scattering: The non-luminous object blocks some light and reflects the rest.
Detection: The reflected light rays travel into our eyes, allowing us to see the object.

Sequence B: The Chronological Progression of Shadows During a Day

Sunrise (Morning):
- Sun’s Position: Low in the sky (East).
- Resulting Shadow: Extremely long and projected toward the West.
Midday (Noon):
- Sun’s Position: High and directly overhead.
- Resulting Shadow: Extremely short and small.
Sunset (Evening):
- Sun’s Position: Low in the sky (West).
- Resulting Shadow: Extremely long and projected toward the East.
Night (No Sun):
- Light Source: The Sun is absent.
- Resulting Shadow: Natural daytime shadows disappear; shadows can now only be formed by human-made luminous sources, like a candle in a room.

Sequence C: The Chain of Sound Production and Transmission

Mechanical Disturbance: An action occurs, such as a spoon striking a steel plate or air passing through human vocal cords.
Vibration: The physical object begins to move continuously and rapidly back and forth (vibrates).
Medium Interaction: The vibrating object pushes against the surrounding air molecules.
Wave Transmission: The vibrations travel through the air in all directions.
Velocity: The sound waves travel through the air at a rapid speed of around 1,235 per hour.
Auditory Perception: The waves reach our ears, where they are converted into the sounds we perceive.
The Vacuum Exception: If this process is attempted on the Moon, Step 3 fails because there is no air, breaking the sequence and resulting in complete silence.

Sequence D: The Execution of Force

Applied Effort: An entity exerts physical effort in the form of a push (shoving away) or a pull (towing closer).
Contact and Resistance: The force is transferred directly to the target object.
Physical Response:
- If at rest: The object overcomes inertia and begins to move.
- If in motion: The object is brought to a stop or is deflected into a new direction.
- If structurally flexible: The internal particles of the object shift, resulting in a change of shape.

Comprehensive Vocabulary (The Word List)

Every key physical and scientific term from the chapter is extracted, defined, and contextualized below:

Luminous – An object that gives out or emits light of its own. – Used in this chapter to define and classify light-giving sources like the Sun, stars, candles, and lamps.
Non-luminous – An object that does not give out light of its own. – Referenced to describe everyday objects like watches, pens, pencils, tables, and the Moon, which can only be seen when light falls on them.
Light – A form of energy that travels in straight lines and enables us to see the objects in our surroundings. – Serves as the primary focus of the chapter’s first section, explaining how human vision works.
Shadow – A dark patch or shape formed on a surface when an object blocks the path of light. – Discussed in detail to show how shadows change in size and position during the day according to the Sun’s location.
Vibrating objects – Objects that move continuously and rapidly back and forth. – Introduced to explain the mechanical source of all sounds in our surroundings.
Noise – A sound that is loud and highly unpleasant to human ears. – Used in the text to describe the harmful and disturbing sound made when many people talk loudly at the same time in classrooms, theatres, markets, or fairs.
Force – A push or pull applied to an object that causes it to move, stop, or change its direction or shape. – Explains the core mechanical principle behind physical actions in our daily lives.
Push – An applied force that drives an object away from the source of the force. – Illustrated in the chapter by a boy pushing a door.
Pull – An applied force that draws an object closer to the source of the force. – Illustrated in the chapter by a man pulling a trolley.
Moon – Earth’s natural satellite, which has no light of its own and lacks an atmosphere. – Used in the text for two critical science facts: it is non-luminous (reflecting sunlight), and sound cannot travel on it due to the lack of air.
Sun – The giant star at the center of our solar system. – Identified in this chapter as the primary natural source of light on the Earth.

Teacher’s Chapter Checklist

This rigorous instructional roadmap outlines every core target, concept, and factual milestone required for curriculum mastery:

[ ] Introduction to Sensory Inputs: Ensure students understand that we see with light, hear sounds with ears, and move items with force.
[ ] Luminous Objects (Definition & Examples): Define as objects emitting their own light; identify the Sun and stars as natural examples.
[ ] Human-Made Luminous Sources: Identify candles, lamps, and diyas as human-made light sources.
[ ] Non-Luminous Objects (Definition & Examples): Define as objects that do not emit light; identify watches, pens, pencils, tables, chairs, and paper as examples.
[ ] The Moon’s Non-Luminous Nature: Explain that the Moon lacks its own light and only reflects the Sun’s light.
[ ] Rectilinear Propagation of Light: Teach that light travels in straight lines (rays), cannot bend, and can only be blocked.
[ ] Shadow Formation Mechanics: Explain that shadows form when an object blocks light, always projecting on the opposite side of the light source.
[ ] Shadow Size & Position Variations: Map out how shadows change throughout the day based on the Sun’s position (long in morning/evening, short at noon).
[ ] Indoor Shadow Phenomenon: Note that shadows are also formed by candle light in a room.
[ ] Sound Production via Vibration: Teach that sound is produced by vibrating (continuously moving) objects.
[ ] Everyday Examples of Sound: Reference the sound of a spoon hitting a steel plate and water being poured into a glass.
[ ] Anatomical Sound Production: Explain that the human tongue helps in producing different sounds when we talk.
[ ] Categories of Sounds: Differentiate between soft, loud, pleasant, and unpleasant sounds.
[ ] Pleasant Sound Examples: Identify the flute and piano as sources of pleasant sounds.
[ ] Noise Definition & Hazards: Define noise as loud, unpleasant sound; emphasize that it is harmful to health and disturbs everyone.
[ ] Noisy Environments: List public places, theatres, fairs, markets, and loud classrooms as typical sources of noise.
[ ] Noise Mitigation Habits: Instruct students to speak softly, play TV/music at low volumes, and avoid using car horns.
[ ] Speed of Sound in Air: Ensure students know the factual figure (around 1,235 per hour).
[ ] Sound Transmission Limitation: Explain that sound does not travel on the Moon because there is no air.
[ ] Force Definition: Define force strictly as a push or a pull.
[ ] Daily Actions Involving Force: Connect force to pushing a door or pulling a trolley.
[ ] The Four Major Effects of Force:
- [ ] Can move an object.
- [ ] Can stop a moving object.
- [ ] Can change the direction of a moving object.
- [ ] Can change the shape of an object.

Ready-Reckoner Student Revision Notes

A comprehensive, high-density study guide designed for exam preparation.

UNIT 1: LIGHT AND ITS PROPERTIES

1. Understanding Light and Vision

Core Purpose: Light is a form of energy that allows us to see the objects in our surroundings. Without light, our eyes cannot perceive any objects.
How Light Travels: Light travels in a straight line in the form of rays.
The Non-Bending Rule: Light cannot bend around obstacles; it can only be blocked. It continues to travel in a straight path until it collides with an object.

2. Luminous vs. Non-Luminous Objects

Objects are classified based on their ability to emit light:

Luminous Objects:
- Definition: Objects that give out/emit light of their own.
- Natural Luminous Objects: The Sun (the main source of light on the Earth) and the stars.
- Human-Made Luminous Objects: Lamps, candles, and diyas.
Non-Luminous Objects:
- Definition: Objects that do not give out light of their own. We can only see them when light from a luminous source falls on them.
- Examples: Watches, pens, pencils, tables, chairs, and paper.
- The Moon: The Moon is non-luminous. It does not have light of its own and only reflects the Sun’s light that falls on it.

3. The Science of Shadows

How a Shadow Forms: A shadow is a dark patch or shape formed on a surface (like the ground or a wall) when the path of light is blocked by an object.
Position: A shadow is always formed on the opposite side of the source of light.
Changing Sizes and Positions: The size and position of a shadow change continuously during the day according to the position of the Sun:
- Morning and Evening: The Sun is low in the sky, making shadows longer than the actual object.
- Noon (Midday): The Sun is directly overhead, making shadows very short and small.
- Candle Light: Shadows can also be formed indoors in candle light.

UNIT 2: THE SCIENCE OF SOUND

1. How Sound is Created

Definition of Sound: Sound is a form of energy that we hear with our ears.
Vibrations: Sound is produced by vibrating objects. To vibrate means to move continuously and rapidly back and forth.
Vocal Sounds: When humans talk, our tongue helps in producing different types of sounds.
Everyday Examples of Sound:
- Eating from a steel plate with a spoon.
- Pouring water out of a container into a glass.

2. Classification of Sounds

Sounds around us can be divided into distinct categories:

Soft Sounds: Gentle, quiet sounds.
Pleasant Sounds: Sounds that are lovely to hear, such as the sound of a flute or a piano.
Loud Sounds: Strong, high-volume sounds.
Unpleasant Sounds / Noise:
- Definition: Sound that is loud and unpleasant to human ears is called noise.
- Sources: Children shouting in a class, crowds in a theatre, fairs, markets, public places, jet planes, firecrackers, and drilling machines.
- Health Hazards: Noise is harmful to health and disturbs everyone. It is not healthy for us.

3. Protecting Our Ears (Acoustic Rules)

To reduce harmful noise, we must practice good habits:

We should speak softly.
We must watch television and listen to music at a low volume.
We should avoid using car horns.

4. Key Physics Facts of Sound

Speed of Sound: Sound travels through the air at a speed of around 1,235 per hour.
The Space Barrier: Sound requires a medium (like air) to travel. Because there is no air on the Moon, sound does not travel on the Moon’s surface.

UNIT 3: FORCE AND MOTION

1. What is Force?

Definition: A force is a push or pull applied to an object.
Application: We push or pull things by applying physical force.
- Push: Moving an object away from you (e.g., a boy pushing a door).
- Pull: Moving an object closer to you (e.g., a man pulling a luggage trolley).

2. The Four Effects of Force

Force is the ultimate modifier of movement and shape. It has four core effects:

Force can move an object: It causes a stationary object (at rest) to start moving.
Force can stop a moving object: It can halt an object that is in motion.
Force can change the direction of a moving object: It can deflect a moving object into a different path.
Force can change the shape of an object: It can compress, stretch, or bend an object (like squeezing dough or clay).

UNIT 4: QUICK EXAM STUDY MATRIX

Question Type	Practice Question	Correct Exam Answer	Grounding Source
Fact Check	Does light travel in a curved line?	No. Light travels only in a straight line.	Passage
Fact Check	Is the Moon a luminous object?	No. It is non-luminous; it only reflects sunlight.	Passage
Fact Check	Can sound travel on the Moon?	No. There is no air on the Moon for sound to travel.	Passage
Vocabulary	What are vibrating objects?	Objects that move continuously.	Passage
Vocabulary	What is noise?	Sound that is loud and unpleasant to human ears.	Passage
Habit Check	Should we encourage or avoid horns?	We should avoid using horns.	Passage
Mechanical	Give an example of pulling force.	A man pulling a trolley.	Passage
Mechanical	Give an example of pushing force.	A boy pushing a door.	Passage

QUESTIONS :

Master Question Bank: Light, Sound and Force

1. The “Hidden” In-Text Questions (Mid-Chapter Extraction)

Q1. From the introductory “Let’s Begin” section, identify the three physical inputs or experiences we encounter in daily life and specify the sensory organ or physical action associated with each as mentioned in the text.

Q2. According to the “Sources of Light” section, how are luminous objects defined, and what are the three human-made examples of luminous objects explicitly listed in the text?

Q3. Based on the description of non-luminous objects, explain why we are able to see a watch, pen, pencil, table, chair, or paper, and what physical event must occur for them to become visible to our eyes.

Q4. Explain the physical mechanism by which the Moon is visible to us in the night sky, despite having no light-producing capabilities of its own.

Q5. Analyze the statement “Light travels in a straight line in the form of rays.” What does the text state that light cannot do, and under what condition does it stop traveling in a straight line?

Q6. How does the text define a shadow, and what is the exact physical cause and spatial orientation (position) of its formation relative to the light source?

Q7. Explain how the size and position of an object’s shadow change during the day, and what celestial factor dictates these continuous variations.

Q8. According to the text, what everyday dining and kitchen actions produce sounds, and what is the underlying mechanical source of all sounds in our surroundings?

Q9. What anatomical structure helps humans in producing different sounds when they talk, according to the “Sound” section?

Q10. How does the chapter define noise, and what public and social settings are explicitly listed as places where noise is produced when everyone talks loudly at the same time?

Q11. According to the “Noise” section, why is noise harmful, and what three specific personal acoustic practices does the text recommend to protect health and maintain quietness?

Q12. What is the numerical value given for the speed of sound in air, and what physical medium is required for sound to travel?

Q13. Explain why sound is unable to travel on the surface of the Moon, referring to the physical atmosphere of the Moon as detailed in the text.

Q14. Define force as explained in the “Force” section, and specify the two primary daily actions through which force is applied to move or stop objects.

Q15. List the four major physical effects of force on an object as outlined in the text.

2. The Textbook Exercise Integration (Back-of-Chapter)

Let’s Say: Give one word answer.

It travels in a straight line.
These objects give us light.
It can change the shape of an object.

Let’s Write:

A. Tick (✔) the correct option.

The objects which give out light of their own are called : (a) Non-luminous objects (b) Luminous objects (c) Both of these (d) None of these
Watch, pen and pencil are examples of: (a) Non-luminous objects (b) Luminous objects (c) Lighted objects (d) Transparent objects
Which of the following is a pleasant sound? (a) Sound of jet planes (b) Sound of crackers (c) Sound of a drilling machine (d) Sound of a flute
A force is : (a) Touch or rub each other (b) Repel each other (c) A push or pull (d) None of these

B. Fill in the blanks using the words from the help box.

[ears, blocked, candle, noise]

Shadows are formed when the path of light is ________.
Sound that is loud and unpleasant to humans ________ is called noise.
________ is not healthy for us.
________ is a human-made luminous object.

C. Write ‘T’ for true and ‘F’ for false statements.

All the objects around us are luminous.
Sound is produced due to vibration.
Force is a push or pull that moves, stops or changes the shape of an object.
Light travels in a curved line.

D. Match the columns. Column A:

Pulling a trolley
Pleasant sound
Noise
Sun Column B: (a) Source of light (b) Children shouting in the class (c) An example of force (d) Playing the piano

E. Answer the following questions.

What is a luminous object? Give two examples of luminous objects.
What is force? How does it help in our daily life?
What is noise? How is a sound produced?
Name the main source of light on Earth.

Mind Maze [HOTS]

Is the Moon a luminous object?

Learning Application – Picture-based Question Look at the pictures given below and write the different kinds of sounds that are produced. [Pictures 1, 2, 3, 4]

Life Skills – Scientific Enquiry Observe your shadows at different times of the day. Note down the times and variations in the length of the shadows. Try to find out the reasons for these changes.

Project/Activity – Experiential Learning

Collect different items like paper, spoons, cardboard, wood, plastic, pens, coins and glass. Set up a screen and ask your friend to sit on the other side. Make sounds with the materials you have collected and ask your friend to guess which material is making each sound.
Ask the students to create these shadows on the wall using a torch.

Junior Scientist – Give two examples of each:

Luminous objects
Non-luminous objects
Unpleasant sounds
Pleasant sounds

3. Exhaustive Objective Bank (The Factual Baseline)

Q1. Which of the following is defined as the main source of light on the Earth?

A) The Moon B) The Sun C) Burning candles D) Stars

Q2. What are objects called that do not emit light of their own? A) Luminous objects B) Non-luminous objects C) Lighted objects D) Transparent objects

Q3. In what form does light travel according to the textbook?

A) Waves B) Curved lines C) Rays D) Shaded patches

Q4. What is the silvery light of the Moon in reality?

A) Its own light B) Reflected light of the Sun C) Bioluminescence D) Light from the stars

Q5. A dark patch formed on the ground when light is blocked by an object is called what?

A) Ray B) Reflection C) Shadow D) Luminous patch

Q6. On which side of the light source is a shadow always formed

? A) The same side B) The opposite side C) The left side only D) The right side only

Q7. How does a shadow’s size and position change during the day?

A) According to the size of the object B) According to the speed of the wind C) According to the position of the Sun D) It remains completely unchanged

Q8. Which of the following is a human-made luminous object mentioned in the text?

A) Star B) Pen C) Diya D) Table

Q9. Which set of items contains only non-luminous objects according to the textbook?

A) Sun, candle, diya B) Watch, pen, pencil C) Lamp, paper, star D) Candle, watch, table

Q10. How is sound produced according to the scientific explanation in the text?

A) By non-luminous objects B) By vibrating objects C) By straight rays D) By applying pulling forces

Q11. What anatomical part helps humans in producing different sounds when they talk?

A) Ears B) Teeth C) Tongue D) Throat

Q12. According to the textbook, what is the speed of sound in air?

A) Around 343 meters per second B) Around 1,235 per hour C) Around 300,000 kilometers per second D) Around 100 miles per hour

Q13. Why does sound not travel on the Moon’s surface?

A) Because there is no light on the Moon B) Because there is no gravity on the Moon C) Because there is no air on the Moon D) Because the Moon is non-luminous

Q14. What is sound that is loud and unpleasant to human ears called?

A) Pleasant sound B) Soft sound C) Noise D) Vibration

Q15. Which of the following is identified as a pleasant sound in the textbook?

A) Children shouting in the class B) Sound of a drilling machine C) Sound of a flute D) Sound of a jet plane

Q16. Where is noise produced when everyone starts talking loudly at the same time?

A) Only in a classroom B) Only in a theatre or fair C) Only in a market D) In a public place, theatre, fair, market, or classroom

Q17. Which of the following is a physical habit recommended in the textbook to protect health from noise?

A) Speaking loudly B) Watching television at a high volume C) Speaking softly D) Encouraging the use of horns

Q18. What is defined as a push or pull that causes an object to move or stop moving?

A) Vibration B) Shadow C) Force D) Light

Q19. Which of the following is an example of a “pull” given in the textbook?

A) A boy pushing a door B) Squeezing dough C) A man pulling a trolley D) Blowing a flute

Q20. What physical change can a force cause in an object, such as modeling clay or dough?

A) Change in its light emission B) Change in its shape C) Change in its speed of sound D) It cannot cause any physical change

Q21. What are “vibrating objects” according to the glossary (Science Word) in the textbook?

A) Objects that do not emit light B) Objects that move continuously C) Objects that block the path of light D) Objects that are pushed or pulled

Q22. Which of the following is NOT an effect of force mentioned in the textbook?

A) Move an object B) Stop a moving object C) Change the direction of a moving object D) Make an object luminous

Fill in the Blanks:

Q23. The Sun is the ______ source of light on the Earth.

Q24. Human-made objects such as lamp, candle or ______ are other light giving objects.

Q25. Most of the objects around us are ______ objects and do not emit their own light.

Q26. The Moon does not have light of its own; it ______ the light of the Sun that falls on it.

Q27. Light travels in a straight line in the form of ______.

Q28. Light does not bend, but can only be ______.

Q29. A shadow is formed on the ______ side of the source of light.

Q30. The shadow changes its size and position during the day according to the position of the ______.

Q31. Sound is produced by ______ objects.

Q32. Our ______ helps in producing different sounds when we talk.

Q33. Sound that is loud and unpleasant to human ears is called ______.

Q34. The speed of sound in air is around ______ per hour.

Q35. As there is no ______ on the Moon, sound does not travel on the Moon’s surface.

Q36. A force is a push or ______ that causes an object to move or stop moving.

Q37. We should watch television and listen to music at a ______ volume.

True or False (If False, correct the statement):

Q38. All the objects around us are luminous. (If False, correct the statement)

Q39. Light travels in a curved line. (If False, correct the statement)

Q40. Shadows are formed on the same side of the source of light. (If False, correct the statement)

Q41. The Moon does not have light of its own and reflects sunlight. (If False, correct the statement)

Q42. Sound is produced due to vibration. (If False, correct the statement)

Q43. Noise is good for our health. (If False, correct the statement)

Q44. We should encourage the use of car horns to clear traffic. (If False, correct the statement)

Q45. Sound can travel easily on the Moon because of its gravity. (If False, correct the statement)

Q46. Force can change the shape of an object. (If False, correct the statement)

Q47. A watch, pen, and pencil are examples of luminous objects. (If False, correct the statement)

4. Subjective & Competency Bank (Higher-Order Thinking)

Short-Answer Questions:

Q48. Explain how we are able to see non-luminous objects like tables, chairs, and pens around us.

Q49. Why is the Moon classified as a non-luminous object even though it appears bright in the night sky?

Q50. How is a shadow formed when we walk outside on a sunny day?

Q51. Explain how the size and position of a shadow change from morning to noon and then to evening.

Q52. Why does light form a shadow when it hits an opaque object instead of bending around it?

Q53. How is sound produced when we talk or hit a steel plate with a spoon?

Q54. Explain the difference between pleasant sounds and noise, giving examples of each.

Q55. Why is noise considered harmful to human health and what are some ways to reduce it?

Q56. How does force help us in our daily activities like opening doors or carrying luggage?

Q57. Why are we unable to hear any sounds on the surface of the Moon?

Scenario-Based / Competency Questions:

Q58. Imagine you are in a dark room with a watch, a pen, and an unlit candle; explain step-by-step how lighting the candle allows you to see the non-luminous watch and pen.

Q59. A student stands in a playground at 8:00 AM, 12:00 PM, and 4:00 PM; describe how their shadow changes in length and direction at these times and explain why.

Q60. In a noisy classroom where everyone talks loudly at once, explain what type of sound is created, why it is harmful, and what steps students should take instead.

Q61. An astronaut on the Moon tries to talk to a teammate by shouting; explain why the teammate cannot hear anything and what scientific fact about sound explains this.

Q62. A chef is working with modeling clay and a rolling pin; explain how the chef uses push and pull forces to change the motion of the rolling pin and the shape of the clay.

Long-Answer / Essay Questions:

Q63. Detail the properties of light as discussed in the chapter, focusing on how it travels, how it interacts with luminous and non-luminous objects, and the mechanics of shadow formation.

Q64. Provide a comprehensive classification of sounds, detailing how sounds are produced, the difference between pleasant and unpleasant sounds, and the specific daily practices required to mitigate noise pollution.

Q65. Define force, describe the two main ways force is applied, and thoroughly explain the four major effects that force can have on an object with examples from the text.

Q66. Compare and contrast the physical conditions on Earth and the Moon regarding both light and sound, explaining why the Moon appears bright but remains completely silent.

Q67. Explain the entire sequence of cause-and-effect that occurs from the moment a physical object starts vibrating to the moment we hear a sound, including the speed of sound and medium constraints.

5. The Master Answer Key & Marking Rubric

Part 1: “Hidden” In-Text Questions (Answers)

Q1. Answer:

The three physical experiences and their associated organs/actions are:
1. Seeing things around us, which is done with the help of light.
2. Hearing different kinds of sounds, which is done with our ears.
3. Moving things, which is done by pushing or pulling them (applying force).

Q2. Answer:

Luminous objects are light-giving objects that emit/give out light of their own.
The three human-made examples of luminous objects explicitly listed are: lamp, candle, and diya.

Q3. Answer:

We see non-luminous objects (like watches, pens, pencils, tables, chairs, and paper) only when light from a luminous source falls on them and reflects into our eyes.
Because they do not emit their own light, they are invisible until they reflect light from an active source.

Q4. Answer:

The Moon does not have light of its own (it is non-luminous).
It is visible to us because it reflects the light of the Sun that falls on it.

Q5. Answer:

The text states that light does not bend.
Light continues to travel in a straight line until it hits something (at which point it is blocked or reflected).

Q6. Answer:

A shadow is defined as a dark patch (or shape) formed on a surface when the path of light is blocked by an object.
It is always formed on the opposite side of the source of light.

Q7. Answer:

The shadow changes its size and position during the day according to the position of the Sun.
It can be bigger or smaller than the actual object.

Q8. Answer:

Everyday actions that make sound include: Eating food from a steel plate with a spoon, or pouring/taking out water from a container in a glass.
The underlying mechanical source of all sounds is vibrating objects.

Q9. Answer:

Our tongue helps in producing different sounds when we talk.

Q10. Answer:

Noise is defined as sound that is loud and unpleasant to human ears.
Public and social settings listed include: public places, theatres, fairs, markets, and classrooms.

Q11. Answer:

Noise is harmful because it is harmful for health and disturbs everyone.
The three recommended practices are:
1. We should speak softly.
2. We should watch television and listen to music at a low volume.
3. We should avoid the use of horns.

Q12. Answer:

The speed of sound in air is around 1,235 per hour.
Sound requires a medium, specifically air, to travel.

Q13. Answer:

Sound does not travel on the Moon’s surface because there is no air on the Moon.
Since sound travels through vibrations in the air, the lack of air prevents sound waves from transmitting.

Q14. Answer:

Force is a push or pull that causes an object to move or stop moving.
The two primary actions are pushing (moving away, e.g., pushing a door) and pulling (moving closer, e.g., pulling a trolley).

Q15. Answer:

The four effects of force are:
1. It can move an object.
2. It can stop a moving object.
3. It can change the direction of a moving object.
4. It can change the shape of an object.

Part 2: Textbook Exercise Integration (Answers)

Let’s Say: Give one word answer.

Light
Luminous objects
Force

Let’s Write: A. Tick (✔) the correct option.

(b) Luminous objects
(a) Non-luminous objects
(d) Sound of a flute
(c) A push or pull

B. Fill in the blanks using the words from the help box.

blocked
ears
Noise
candle

C. Write ‘T’ for true and ‘F’ for false statements.

F (Most of the objects around us are non-luminous, like watch, pen, table, chair, etc.)
T
T
F (Light travels in a straight line, it does not bend)

D. Match the columns.

Pulling a trolley -> (c) An example of force
Pleasant sound -> (d) Playing the piano
Noise -> (b) Children shouting in the class
Sun -> (a) Source of light

E. Answer the following questions.

Luminous object: An object that gives out/emits light of its own. Examples: Sun, stars, candle, lamp.
Force: A push or pull that causes an object to move or stop moving, or change its shape or direction. It helps us in daily life by moving doors, pulling luggage trolleys, and shifting objects.
Noise: Sound that is loud and unpleasant to human ears. Sound production: Sound is produced by vibrating objects (objects that move continuously).
Main source of light on Earth: The Sun.

Mind Maze [HOTS]

Answer: No, the Moon is not a luminous object. It does not have light of its own and only reflects the Sun’s light.

Learning Application – Picture-based Question

Possible answers based on text concepts of sound types:
1. Soft/Pleasant sound
2. Loud/Unpleasant sound
3. Pleasant sound
4. Loud sound/Noise

Junior Scientist – Give two examples of each:

Luminous objects: Sun, stars.
Non-luminous objects: Watch, pen.
Unpleasant sounds: Sound of jet planes, sound of crackers.
Pleasant sounds: Sound of a flute, playing the piano.

Part 3: Exhaustive Objective Bank (Answers)

MCQs (Answers):

Q1: B
Q2: B
Q3: C
Q4: B
Q5: C
Q6: B
Q7: C
Q8: C
Q9: B
Q10: B
Q11: C
Q12: B
Q13: C
Q14: C
Q15: C
Q16: D
Q17: C
Q18: C
Q19: C
Q20: B
Q21: B
Q22: D

Fill in the Blanks (Answers):

Q23. main
Q24. diya
Q25. non-luminous
Q26. reflects
Q27. rays
Q28. blocked
Q29. opposite
Q30. Sun
Q31. vibrating
Q32. tongue
Q33. noise
Q34. 1,235
Q35. air
Q36. pull
Q37. low

True or False Statements (Corrected Answers):

Q38: False. Most of the objects around us are non-luminous (e.g., watch, pen, pencil, table, chair, paper). Only some are luminous.
Q39: False. Light travels in a straight line, it does not bend or travel in a curved line.
Q40: False. Shadows are always formed on the opposite side of the source of light.
Q41: True.
Q42: True.
Q43: False. Noise is harmful for health and disturbs everyone; it is not healthy/good for our health.
Q44: False. We should avoid the use of horns to prevent noise pollution.
Q45: False. Sound does not travel on the Moon’s surface because there is no air on the Moon.
Q46: True.
Q47: False. A watch, pen, and pencil are non-luminous objects because they do not emit their own light.

Part 4: Subjective & Competency Bank (Marking Rubrics)

Short-Answer Questions (Rubrics)

Q48. Rubric (Visible Non-Luminous Objects):

Marks Distribution (Total: 2 Marks):
- 1 Mark for explaining that non-luminous objects do not emit light of their own.
- 1 Mark for stating that we see them only when light from a luminous source falls on them and reflects into our eyes.
Source Section: “Sources of Light”.

Q49. Rubric (Moon as Non-Luminous):

Marks Distribution (Total: 2 Marks):
- 1 Mark for stating that the Moon does not have its own light.
- 1 Mark for explaining that it only reflects the light of the Sun that falls on it.
Source Section: “Light Travels in a Straight Line”.

Q50. Rubric (Shadow Formation):

Marks Distribution (Total: 2 Marks):
- 1 Mark for explaining that light travels in straight lines and cannot bend.
- 1 Mark for stating that when our body blocks the path of light, a dark patch (shadow) is formed on the ground on the opposite side of the Sun.
Source Section: “Shadow”.

Q51. Rubric (Shadow Variation):

Marks Distribution (Total: 3 Marks):
- 1 Mark for explaining that shadows change size and position according to the Sun’s position.
- 1 Mark for stating that in the morning and evening, the Sun is low in the sky, creating longer shadows.
- 1 Mark for stating that at noon, the Sun is directly overhead, creating very short and small shadows.
Source Section: “Shadow”.

Q52. Rubric (Opaque Blocking vs Bending):

Marks Distribution (Total: 2 Marks):
- 1 Mark for explaining that light travels strictly in straight lines in the form of rays.
- 1 Mark for stating that because light cannot bend around obstacles, it is completely blocked, resulting in a dark shape/patch behind the object.
Source Section: “Light Travels in a Straight Line”.

Q53. Rubric (Sound Production):

Marks Distribution (Total: 2 Marks):
- 1 Mark for stating that sound is produced by vibrating objects.
- 1 Mark for explaining that hitting an object (like a plate with a spoon) or talking causes continuous rapid motion (vibrations) that travel through the air.
Source Section: “Sound”.

Q54. Rubric (Pleasant Sound vs Noise):

Marks Distribution (Total: 2 Marks):
- 1 Mark for defining pleasant sounds as soft and lovely to hear (e.g., flute, piano).
- 1 Mark for defining noise as loud and unpleasant sounds (e.g., shouting, drilling machines).
Source Section: “Types of Sounds” / “Noise”.

Q55. Rubric (Noise Hazards & Mitigation):

Marks Distribution (Total: 3 Marks):
- 1 Mark for explaining that noise is harmful to health and disturbs everyone.
- 2 Marks (1 Mark each for any two habits): Speaking softly, keeping TV/music volume low, or avoiding car horns.
Source Section: “Noise”.

Q56. Rubric (Force Daily Utility):

Marks Distribution (Total: 2 Marks):
- 1 Mark for defining force as a push or pull.
- 1 Mark for giving examples of how force helps us: moving things (pushing doors) and stopping/carrying things (pulling trolleys).
Source Section: “Force”.

Q57. Rubric (Silence on the Moon):

Marks Distribution (Total: 2 Marks):
- 1 Mark for stating that sound requires a medium (specifically air) to travel.
- 1 Mark for explaining that because there is no air on the Moon, sound cannot travel on the Moon’s surface.
Source Section: “Force” (Fact Flash).

Scenario-Based / Competency Questions (Rubrics)

Q58. Rubric (Dark Room & Candle Scenario):

Marks Distribution (Total: 3 Marks):
- 1 Mark for identifying that the watch, pen, and unlit candle are non-luminous and cannot emit light.
- 1 Mark for explaining that lighting the candle makes it a luminous object that emits light rays in straight lines.
- 1 Mark for explaining that these rays fall on the non-luminous watch and pen and reflect into our eyes, making them visible.
Source Section: “Sources of Light”.

Q59. Rubric (Shadow Playground Scenario):

Marks Distribution (Total: 3 Marks):
- 1 Mark (8:00 AM): Shadow is long and pointed toward the West because the Sun is low in the East.
- 1 Mark (12:00 PM): Shadow is very short and small directly under the student because the Sun is overhead.
- 1 Mark (4:00 PM): Shadow is long and pointed toward the East because the Sun is low in the West.
Source Section: “Shadow”.

Q60. Rubric (Noisy Classroom Scenario):

Marks Distribution (Total: 3 Marks):
- 1 Mark for identifying that everyone talking loudly at once creates noise (loud and unpleasant sound).
- 1 Mark for stating that this noise is harmful to health and highly disturbing.
- 1 Mark for recommending that students speak softly and avoid shouting.
Source Section: “Noise”.

Q61. Rubric (Astronaut Shouting Scenario):

Marks Distribution (Total: 3 Marks):
- 1 Mark for stating that sound is produced by vibrating objects and needs air to propagate.
- 1 Mark for highlighting the physical fact that there is no air on the Moon.
- 1 Mark for concluding that without air, the vibrations cannot travel to the teammate’s ears, resulting in total silence.
Source Section: “Force” (Fact Flash).

Q62. Rubric (Chef Clay & Rolling Pin Scenario):

Marks Distribution (Total: 3 Marks):
- 1 Mark for explaining that pushing/pulling the rolling pin applies a force that moves it across the table.
- 1 Mark for explaining that applying force to the clay (pressing, rolling, squeezing) changes its shape.
- 1 Mark for identifying that force is the push or pull that alters both motion and physical structure.
Source Section: “Force”.

Long-Answer / Essay Questions (Rubrics)

Q63. Rubric (Comprehensive Properties of Light):

Marks Distribution (Total: 5 Marks):
- 1 Mark for explaining that light travels strictly in straight lines as rays and does not bend.
- 1 Mark for distinguishing between luminous (emits own light, e.g., Sun, stars) and non-luminous objects (cannot emit light, e.g., watch, pencil).
- 1 Mark for explaining the reflective role of the Moon.
- 1 Mark for defining a shadow as a dark patch formed when light is blocked by an opaque object.
- 1 Mark for noting that shadows form on the opposite side of the light source.
Source Section: “Sources of Light”, “Light Travels in a Straight Line”, “Shadow”.

Q64. Rubric (Classification & Mitigation of Sounds):

Marks Distribution (Total: 5 Marks):
- 1 Mark for explaining that sound is produced by vibrations (continuous rapid movement).
- 1 Mark for detailing the types of sounds: soft, loud, pleasant, and unpleasant.
- 1 Mark for defining noise as loud, unpleasant sound that is harmful to health.
- 2 Marks (1 Mark each for any two daily mitigation actions): Speaking softly, playing TV/music at low volume, avoiding car horns.
Source Section: “Sound”, “Types of Sounds”, “Noise”.

Q65. Rubric (Force, Action Types, and Four Effects):

Marks Distribution (Total: 5 Marks):
- 1 Mark for defining force as a push or pull that moves or stops objects.
- 1 Mark for illustrating the two action types: push (moving away, e.g., boy pushing door) and pull (moving closer, e.g., man pulling trolley).
- 3 Marks (1 Mark each for any three detailed effects with examples):
  - Force can move a stationary object.
  - Force can stop or change the direction of a moving object.
  - Force can change the shape of an object (e.g., modeling clay or dough).
Source Section: “Force”.

Q66. Rubric (Earth vs Moon Environmental Physics Comparison):

Marks Distribution (Total: 5 Marks):
- 1 Mark (Light – Earth): Receives abundant light from the Sun (luminous), allowing us to see non-luminous objects.
- 1 Mark (Light – Moon): Is non-luminous and must reflect the Sun’s light to be visible.
- 1 Mark (Sound – Earth): Sound travels easily through the air at around 1,235 per hour because Earth has an atmosphere.
- 1 Mark (Sound – Moon): Sound cannot travel on the Moon because there is no air.
- 1 Mark (Atmospheric Difference Summary): Concludes that while light can travel through a vacuum (allowing sunlight to reflect off the Moon), sound absolutely requires air molecules to propagate, creating a silent lunar landscape.
Source Section: “Light Travels in a Straight Line”, “Sound”, “Force”.

Q67. Rubric (Sound Vibrational Chain of Events):

Marks Distribution (Total: 5 Marks):
- 1 Mark (Initiation): An object undergoes a physical disturbance, causing it to move continuously and rapidly back and forth (vibrate).
- 1 Mark (Mechanical Wave): The vibrating object pushes surrounding air molecules, creating sound waves.
- 1 Mark (Transmission Rate): These waves travel through the air medium at a speed of around 1,235 per hour.
- 1 Mark (Medium Constraint): Emphasizes that this wave transmission requires a medium (like air) and fails on the Moon due to the vacuum.
- 1 Mark (Auditory Reception): The waves strike the human ear, which translates them into audible sounds.
Source Section: “Curiosity Chronicles”, “Sound”, “Force”.